The Crayfish Corps

Imagine this. You’re a student working with crayfish in your biology class. At the end of the year, your teacher decides to give away the specimens. In a good-natured attempt to save them, you release them in a nearby stream. Little do you know that you have unwittingly set loose a true horror on that aquatic ecosystem.

Rusty crayfish, an invasive species in Pennsylvania and many other states, are often spread through release by teachers and students and from biological supply houses. They are also spread through bait bucket release by anglers, aquarium release by hobbyists and the activities of commercial harvesters. Native to the Ohio River Basin, rusty crayfish have expanded their territory all the way from New Mexico to Ontario. Here these crayfish outcompete native species and reduce the aquatic plant abundance and diversity.

In 2008, the rusty crayfish invaded Valley Creek in Valley Forge National Historical Park, which is why Valley Forge created the Crayfish Corps to combat this threat. Their long-term goal is to “maintain a ratio of one rusty crayfish or less for every four native crayfish present in Valley Creek” and they work towards this through volunteer help. It is difficult to manage these pests effectively but there are two ways to start; physically or chemically. While a chemical approach rusty crayfish is more effective than physical removal, these chemicals are not selective and would harm native species. This is why the Crayfish Corps physically remove the invasive species to reduce the population.

I had the pleasure to volunteer in the Crayfish Corps in July. After meeting park ranger, Ellen Bungard, we spent about three hours scouring the creek for any crayfish we could find. We used kick nets to capture crayfish and identified which species each one was using tips provided by the ranger. There are two main ways to identify rusty crayfish, one being the rust-colored spot on their side as their name suggests. The other key feature is the black bands around their claws. By the end of the day we caught 9 rusty crayfish and 117 native species and although that may not sound great, that puts the ratio at one rusty crayfish for thirteen native crayfish. This is great news for Valley Creek but it is only made possible with the help of volunteers, so I urge you to volunteer at Valley Forge if you ever have a free weekend. Below is a link to learn more about the Crayfish Corps.